Layer‐by‐Layer Solution‐Processed Low‐Bandgap Polymer‐PC61BM Solar Cells with High Efficiency

Polymer solar cells (PSCs) are fabricated without solvent additives using a low‐bandgap polymer, PBDTTT‐C‐T, as the donor and [6,6]‐phenyl‐C61‐butyric‐acid‐methyl‐ester (PC₆₁BM) as the acceptor. Donor‐acceptor blend and layer‐by‐layer (LL) solution process are used to form active layers. Relative to the blend devices, the LL devices exhibit stronger absorption, better vertical phase separation, higher hole and electron mobilities, and better charge extraction at correct electrodes. As a result, after thermal annealing the LL devices exhibit an average power conversion efficiency (PCE) of 6.86%, which is much higher than that of the blend devices (4.31%). The best PCE of the LL devices is 7.13%, which is the highest reported for LL processed PSCs and among the highest reported for PC₆₁BM‐based single‐junction PSCs.     

In Situ Generation of Few‐Layer Graphene Coatings on SnO2‐SiC Core‐Shell Nanoparticles for High‐Performance Lithium‐Ion Storage

A simple ball‐milling method is used to synthesize a tin oxide‐silicon carbide/few‐layer graphene core‐shell structure in which nanometer‐sized SnO₂ particles are uniformly dispersed on a supporting SiC core and encapsulated with few‐layer graphene coatings by in situ mechanical peeling. The SnO₂‐SiC/G nanocomposite material delivers a high reversible capacity of 810 mA h g^?1 and 83% capacity retention over 150 charge/discharge cycles between 1.5 and 0.01 V at a rate of 0.1 A g^?1. A high reversible capacity of 425 mA h g^?1 also can be obtained at a rate of 2 A g^?1. When discharged (Li extraction) to a higher potential at 3.0 V (vs. Li/Li⁺), the SnO₂‐SiC/G nanocomposite material delivers a reversible capacity of 1451 mA h g^?1 (based on the SnO₂ mass), which corresponds to 97% of the expected theoretical capacity (1494 mA h g^?1, 8.4 equivalent of lithium per SnO₂), and exhibits good cyclability. This result suggests that the core‐shell nanostructure can achieve a completely reversible transformation from Li_4.4Sn to SnO₂ during discharging (i.e., Li extraction by dealloying and a reversible conversion reaction, generating 8.4 electrons). This suggests that simple mechanical milling can be a powerful approach to improve the stability of high‐performance electrode materials involving structural conversion and transformation.     

Pseudo‐real‐time retinal layer segmentation for high‐resolution adaptive optics optical coherence tomography

We present a pseudo‐real‐time retinal layer segmentation for high‐resolution Sensorless Adaptive Optics‐Optical Coherence Tomography (SAO‐OCT). Our pseudo‐real‐time segmentation method is based on Dijkstra's algorithm that uses the intensity of pixels and the vertical gradient of the image to find the minimum cost in a geometric graph formulation within a limited search region. It segments six retinal layer boundaries in an iterative process according to their order of prominence. The segmentation time is strongly correlated to the number of retinal layers to be segmented. Our program permits en face images to be extracted during data acquisition to guide the depth specific focus control and depth dependent aberration correction for high‐resolution SAO‐OCT systems. The average processing times for our entire pipeline for segmenting six layers in a retinal B‐scan of 496 × 400 and 240 × 400 pixels are around 25.60 and 13.76 ms, respectively. When reducing the number of layers segmented to only two layers, the time required for a 240 × 400 pixel image is 8.26 ms.     

Layer‐by‐Layer Na3V2(PO4)3 Embedded in Reduced Graphene Oxide as Superior Rate and Ultralong‐Life Sodium‐Ion Battery Cathode

Na₃V₂(PO₄)₃ (NVP) is regarded as a promising cathode for advanced sodium‐ion batteries (SIBs) due to its high theoretical capacity and stable sodium (Na) super ion conductor (NASICON) structure. However, strongly impeded by its low electronic conductivity, the general NVP delivers undesirable rate capacity and fails to meet the demands for quick charge. Herein, a novel and facile synthesis of layer‐by‐layer NVP@reduced graphene oxide (rGO) nanocomposite is presented through modifying the surface charge of NVP gel precursor. The well‐designed layered NVP@rGO with confined NVP nanocrystal in between rGO layers offers high electronic and ionic conductivity as well as stable structure. The NVP@rGO nanocomposite with merely ≈3.0 wt% rGO and 0.5 wt% amorphous carbon, yet exhibits extraordinary electrochemical performance: a high capacity (118 mA h g^?1 at 0.5 C attaining the theoretical value), a superior rate capability (73 mA h g^?1 at 100 C and even up to 41 mA h g^?1 at 200 C), ultralong cyclability (70.0% capacity retention after 15 000 cycles at 50 C), and stable cycling performance and excellent rate capability at both low and high operating temperatures. The proposed method and designed layer‐by‐layer active nanocrystal@rGO strategy provide a new avenue to create nanostructures for advanced energy storage applications.     

Chitosan‐heparin polyelectrolyte multilayers on cortical bone: Periosteum‐mimetic,cytophilic, antibacterial coatings

Cortical bone allografts suffer from high rates of failure due to poor integration with host tissue, leading to non‐union, fracture, and infection following secondary procedures. Here, we report a method for modifying the surfaces of cortical bone with coatings that have biological functions that may help overcome these challenges. These chitosan‐heparin coatings promote mesenchymal stem cell attachment and have significant antibacterial activity against both S. aureus and E. coli. Furthermore, their chemistry is similar to coatings we have reported on previously, which effectively stabilize and deliver heparin‐binding growth factors. These coatings have potential as synthetic periosteum for improving bone allograft outcomes. Biotechnol. Bioeng. 2013; 110: 609–618. © 2012 Wiley Periodicals, Inc.     

Multi‐Length‐Scale Morphologies in PCPDTBT/PCBM Bulk‐Heterojunction Solar Cells

Additives are known to improve the performance of organic photovoltaic devices based on mixtures of a low bandgap polymer, poly[2,6‐(4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′]‐dithiophene)‐alt‐4,7‐(2,1,3‐benzothiadiazole)] (PCPDTBT) and [6,6]‐phenyl C61‐butyric acid methyl ester (PCBM). The evolution of the morphology during the evaporation of the mixed solvent, which comprises additive and chlorobenzene (CB), is investigated by in‐situ grazing incidence X‐ray scattering, providing insight into the key role the additive plays in developing a multi‐length‐scale morphology. Provided the additive has a higher vapor pressure and a selective solubility for PCBM, as the host solvent (CB) evaporates, the mixture of the primary solvent and additive becomes less favorable for the PCPDTBT, while completely solubilizing the PCBM. During this process, the PCPDTBT first crystallizes into fibrils and then the PCBM, along with the remaining PCPDTBT, is deposited, forming a phase‐separated morphology comprising domains of pure, crystalline PCPDTBT fibrils and another domain that is a PCBM‐rich mixture with amorphous PCPDTBT. X‐ray/neutron scattering and diffraction methods, in combination with UV–vis absorption spectroscopy and transmission electron microscopy, are used to determine the crystallinity and phase separation of the resultant PCPDTBT/PCBM thin films processed with or without additives. Additional thermal annealing is carried out and found to change the packing of the PCPDTBT. The two factors, degree of crystallinity and degree of phase separation, control the multi‐length‐scale morphology of the thin films and significantly influence device performance.     

High‐Efficiency Low‐Temperature ZnO Based Perovskite Solar Cells Based on Highly Polar,Nonwetting Self‐Assembled Molecular Layers

Herein, this study reports high‐efficiency, low‐temperature ZnO based planar perovskite solar cells (PSCs) with state‐of‐the‐art performance. They are achieved via a strategy that combines dual‐functional self‐assembled monolayer (SAM) modification of ZnO electron accepting layers (EALs) with sequential deposition of perovskite active layers. The SAMs, constructed from newly synthesized molecules with high dipole moments, act both as excellent surface wetting control layers and as electric dipole layers for ZnO‐EALs. The insertion of SAMs improves the quality of PbI₂ layers and final perovskite layers during sequential deposition, while charge extraction is enhanced via electric dipole effects. Leveraged by SAM modification, our low‐temperature ZnO based PSCs achieve an unprecedentedly high power conversion efficiency of 18.82% with a V_OC of 1.13 V, a J_SC of 21.72 mA cm^?2, and a FF of 0.76. The strategy used in this study can be further developed to produce additional performance enhancements or fabrication temperature reductions.     

High Energy Density Sodium‐Ion Battery with Industrially Feasible and Air‐Stable O3‐Type Layered Oxide Cathode

Extensive effort is being made into cathode materials for sodium‐ion battery to address several fatal issues, which restrict their future application in practical sodium‐ion full cell system, such as their unsatisfactory initial Coulombic efficiency, inherent deficiency of cyclable sodium content, and poor industrial feasibility. A novel air‐stable O3‐type Na[Li_0.05Mn_0.50Ni_0.30Cu_0.10Mg_0.05]O₂ is synthesized by a coprecipitation method suitable for mass production followed by high‐temperature annealing. The microscale secondary particle, consisting of numerous primary nanocrystals, can efficiently facilitate sodium‐ion transport due to the short diffusion distance, and this cathode material also has inherent advantages for practical application because of its superior physical properties. It exhibits a reversible capacity of 172 mA h g^?1 at 0.1 C and remarkable capacity retention of 70.4% after 1000 cycles at 20 C. More importantly, it offers good compatibility with pristine hard carbon as anode in the sodium‐ion full cell system, delivering a high energy density of up to 215 W h kg^?1 at 0.1 C and good rate performance. Owing to the high industrial feasibility of the synthesis process, good compatibility with pristine hard carbon anode, and excellent electrochemical performance, it can be considered as a promising active material to promote progress toward sodium‐ion battery commercialization.     

Simultaneous and sensitive detection of dual DNA targets via quantum dot‐assembled amplification labels

We describe a signal amplification assay for the simultaneous detection of HIV‐1 and HIV‐2 via a quantum dot (QD) layer‐by‐layer assembled polystyrene microsphere (PS) composite in a homogeneous format. The crucial point of this composite is the core–shell system. PS is utilized as the core and QDs as the shell. Based on the high affinity of streptavidin and biotin, QDs are assembled layer‐by‐layer on the surface of the PS as amplification labels. Biotinylated reporter probe is combined with the PS–QDs conjugate and then hybridized with target DNA immobilized on the surface of a 96‐well plate. Using this approach, each target DNA corresponds to a large number of QDs and the fluorescence signal is greatly enhanced. Two QD colors (605 and 655 nm) are used to detect dual‐target DNAs simultaneously. Taking advantage of the enzyme‐free reaction and high sensitivity, this PS–QD‐based sensor can be used in simple ‘mix and detection’ assays. Our results show that this technology has potential application in rapid point‐of‐care testing, gene expression studies, high‐throughput screening and clinical diagnostics. Copyright © 2015 John Wiley & Sons, Ltd.     

Overcoming Interfacial Losses in Solution‐Processed Organic Multi‐Junction Solar Cells

Organic solar cells are promising in terms of full‐solution‐processing which enables low‐cost and large‐scale fabrication. While single‐junction solar cells have seen a boost in power conversion efficiency (PCE), multi‐junction solar cells are promising to further enhance the PCE. In all‐solution‐processed multi‐junction solar cells, interfacial losses are often encountered between hole‐transporting layer (HTL) and the active layers and therefore greatly limit the application of newly developed high‐performance donor and acceptor materials in multi‐junction solar cells. Here, the authors report on a systematic study of interface losses in both single‐junction and multi‐junction solar cells based on representative polymer donors and HTLs using electron spectroscopy and time‐of‐flight secondary ion mass spectrometry. It is found that a facile mixed HTL containing poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) and MoO _x nanoparticles successfully overcomes the interfacial losses in both single‐ and multi‐junction solar cells based on various active layers by reducing interface protonation, promoting better energy‐level alignment, and forming a dense and smooth layer. Solution‐processed single‐junction solar cells are demonstrated to reach the same performance as with evaporated MoO _x (over 7%). Multi‐junction solar cells with polymers containing nitrogen atoms as the first layer and the mixed PEDOT:PSS and MoO _x nanoparticles as hole extraction layer reach fill factor (FF) of over 60%, and PCE of over 8%, while the identical stack with pristine PEDOT:PSS or MoO _x nanoparticles show FF smaller than 50% and PCE less than 5%.     

Characterizing the S‐layer structure and anti‐S‐layer antibody recognition on intact Tannerella forsythia cells by scanning probe microscopy and small angle X‐ray scattering

Tannerella forsythia is among the most potent triggers of periodontal diseases, and approaches to understand underlying mechanisms are currently intensively pursued. A ~22‐nm‐thick, 2D crystalline surface (S‐) layer that completely covers Tannerella forsythia cells is crucially involved in the bacterium–host cross‐talk. The S‐layer is composed of two intercalating glycoproteins (TfsA‐GP, TfsB‐GP) that are aligned into a periodic lattice. To characterize this unique S‐layer structure at the nanometer scale directly on intact T. forsythia cells, three complementary methods, i.e., small‐angle X‐ray scattering (SAXS), atomic force microscopy (AFM), and single‐molecular force spectroscopy (SMFS), were applied. SAXS served as a difference method using signals from wild‐type and S‐layer‐deficient cells for data evaluation, revealing two possible models for the assembly of the glycoproteins. Direct high‐resolution imaging of the outer surface of T. forsythia wild‐type cells by AFM revealed a p4 structure with a lattice constant of ~9.0 nm. In contrast, on mutant cells, no periodic lattice could be visualized. Additionally, SMFS was used to probe specific interaction forces between an anti‐TfsA antibody coupled to the AFM tip and the S‐layer as present on T. forsythia wild‐type and mutant cells, displaying TfsA‐GP alone. Unbinding forces between the antibody and wild‐type cells were greater than with mutant cells. This indicated that the TfsA‐GP is not so strongly attached to the mutant cell surface when the co‐assembling TfsB‐GP is missing. Altogether, the data gained from SAXS, AFM, and SMFS confirm the current model of the S‐layer architecture with two intercalating S‐layer glycoproteins and TfsA‐GP being mainly outwardly oriented. Copyright © 2013 John Wiley & Sons, Ltd.     

Evaluation of glucose sensitive affinity binding assay entrapped in fluorescent dissolved‐core alginate microspheres

The feasibility of dissolved‐core alginate‐templated fluorescent microspheres as “smart tattoo” glucose biosensors was investigated in simulated interstitial fluid (SIF). The sensor works on the principle of competitive binding and fluorescence resonance energy transfer. The sensor consists of multilayer thin film coated alginate microspheres incorporating dye‐labeled glucose receptor and competing ligand within the partially dissolved alginate core. In this study, different approaches for the sensing and detection chemistry were studied, and the response of encapsulated reagents was compared with the solution‐phase counterparts. The glucose sensitivity of the encapsulated TRITC‐Con A/FITC‐dextran (500 kDa) assay in DI water was estimated to be 0.26%/mM glucose while that in SIF was observed to be 0.3%/mM glucose. The glucose sensitivity of TRITC‐apo‐GOx/FITC‐dextran (500 kDa) assay was estimated to be 0.33%/mM glucose in DI water and 0.5%/mM glucose in SIF and both demonstrated a response in the range of 0–50 mM glucose. Therefore, it is hypothesized that the calcium ion concentration outside the microsphere (in the SIF) does not interfere with the response sensitivity. The sensor response was observed to exhibit a maximum response time of 120 s. The system further exhibited a sensitivity of 0.94%/mM glucose with a response in range of 0–50 mM glucose, using near‐infrared dyes (Alexa Fluor‐647‐labeled dextran as donor and QSY‐21‐conjugated apo‐GOx as acceptor), thereby making the sensor more amenable to in vivo use, when implanted in scattering tissue. Biotechnol. Bioeng. 2009; 104: 1075–1085. © 2009 Wiley Periodicals, Inc.     

A Cross‐Linked Interconnecting Layer Enabling Reliable and Reproducible Solution‐Processing of Organic Tandem Solar Cells

The performance of tandem organic solar cells (OSCs) is directly related to the functionality and reliability of the interconnecting layer (ICL). However, it is a challenge to develop a fully functional ICL for reliable and reproducible fabrication of solution‐processed tandem OSCs with minimized optical and electrical losses, in particular for being compatible with various state‐of‐the‐art photoactive materials. Although various ICLs have been developed to realize tandem OSCs with impressively high performance, their reliability, reproducibility, and generic applicability are rarely analyzed and reported so far, which restricts the progress and widespread adoption of tandem OSCs. In this work, a robust and fully functional ICL is developed by incorporating a hydrolyzed silane crosslinker, (3‐glycidyloxypropyl)trimethoxysilane (GOPS), into poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and its functionality for reliable and reproducible fabrication of tandem OSCs based on various photoactive materials is validated. The cross‐linked ICL can successfully protect the bottom active layer against penetration of high boiling point solvents during device fabrication, which widely broadens the solvent selection for processing photoactive materials with high quality and reliability, providing a great opportunity to continuously develop the tandem OSCs towards future large‐scale production and commercialization.